1. Field of the Invention
The present invention relates to a semiconductor device including a group of leads, an integrated circuit (IC) chip mounted on one of the leads, a power chip (semiconductor chip) mounted on a die pad, a resin sheet disposed on a bottom side of the die pad to provide insulation, and a resin casing made of a molded resin compound encapsulating all internal elements of the semiconductor device. The invention pertains also to a resin molding die (or mold) used for resin-molding internal elements of such a semiconductor device.
2. Description of the Background Art
A semiconductor device to which the invention is directed is manufactured by a process including bonding semiconductor dies, or chips, such as a power chip and an IC chip, to a leadframe, wire-bonding the power chip and the IC chip to the leadframe, resin-molding all these internal elements of the semiconductor device into a single package.
Wire bonding establishes electrical connections between the power chip and the leadframe by using aluminum wires and between the IC chip and the leadframe by using gold wires. Since the semiconductor device incorporates the power chip which handles a large electric current and generates heat, the semiconductor package must provide high heat dissipation and insulation capabilities.
Conventionally, this kind of semiconductor device is structured as described in Japanese Patent Application Publication No. 2005-123495, for example. Specifically, the semiconductor device disclosed in this Publication is provided with a resin sheet having first and second surfaces disposed on a bottom side of a die pad, the resin sheet forming an insulating layer having at least a specific thickness to provide high insulation quality. Internal elements of the semiconductor device are resin-molded into a single package. The resin sheet is made of resin material whose thermal conductivity is higher than that of a resin molding compound used for encapsulation.
The semiconductor device can provide high heat dissipation and insulation capabilities only if the resin sheet disposed on the back side of the die pad is held in tight adhesion thereto. To make this certain, a resin-molding process of the aforementioned Publication employs a transfer molding technique using a resin molding die (or mold) provided with squeeze pins for forcing the die pad against the resin sheet to hold the die pad in tight contact with the resin sheet during the molding process.
For the semiconductor device designed to handle a large electric current, the molding process performed by using the mold provided with the squeeze pins for forcing the die pad against the resin sheet has a problem that the provision of the squeeze pins results in an increase in size of a molding machine due to the need for pressing the squeeze pins against the die pad.
Additionally, the aforementioned squeeze pin approach of the prior art results in an increased die pad thickness and stiffness. This requires a large-sized apparatus for firmly adhering the die pad to the resin sheet by the squeeze pins.